The following invention reflects ongoing advancement and evolution concerning applicant's earlier U.S. Pat. No. 5,324,480, issued Jun. 28, 1994.
Sample preparations in industrial research and clinical laboratories require many precise pipetting steps, such as: transfer of samples, dilutions, additions of reagents, transfer of reaction mixtures, etc. Automated systems have been developed and are commercially available in the form of programmable pipetting workstations. These automated systems reduce the manual labor involved in the liquid handling and processing of samples.
However, these systems are not completely automatic, because, among other things, they still require manual manipulation of gas regulators in order to provide a specific pressure at appropriate times in the protocol for processing samples.
For example, solid phase extraction often requires multiple steps such as column conditioning, sample loading, washing and elution. Depending on the application, the solvents and samples involved may have different viscosities, different particulate composition and, depending on the protocol step, may require different pressures. The ability to precisely provide and control the various ranges of pressure required during the protocol steps is critical in obtaining good recovery and throughput in the process of solid phase extraction. For example, the loading and elution of samples is typically carried out at low pressure while various other steps are carried out at higher rates of pressure. Existing systems are unable to completely automate and control the various ranges of pressure required in the multiple steps of performing solid phase extraction.
Typically, the user is required to manually operate an air regulator. The regulators have poor accuracy in the middle of the zero to thirty pounds per square inch range and worse accuracy in the critical low pressure range (0 to 2 pounds per square inch). Typically, the user has a manifold of manual air regulators and starts out with the lowest and slowest air pressure as the global pressure setting for requirements of the specific protocol being carried out. The user then turns the regulators by hand to obtain the appropriate pressure required at the appropriate times in the protocol. The result of this is that the current system is, at best, semi-automated and fails to consistently provide good recoveries and throughput.
Therefore, there is a need for an apparatus and method which would be capable of providing continuously adjustable pressure regulators for providing high flows in the case of washing and drying steps and very low flows for sample addition and elution.
The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
______________________________________ U.S. Pat. No. ISSUE DATE INVENTOR ______________________________________ 3,632,119 January 4, 1972 Robert E. Carpenter 3,912,456 October 14, 1975 Robert R. Young 4,677,987 July 7, 1987 Pradip V. Choksi 4,678,752 July 7, 1987 Thorne, et al. 4,679,446 July 14, 1987 Sheehan, et al. 4,730,631 March 15, 1988 Henry L. Schwartz 4,980,297 December 25, 1990 Haynes, et al. 5,078,970 January 7, 1992 Teodorescu, et al. 5,079,170 January 7, 1992 Rosman, et al. 5,169,120 December 8, 1992 Guthrie, et al. 5,322,626 June 21, 1994 Frank, et al. 5,324,480 June 28, 1994 Shumate, et al. ______________________________________